Friction-engaging device

ABSTRACT

Herein disclosed is a friction-engaging device such as a friction clutch for motor vehicle power transmission systems, having a flywheel which is made up of main and subsidiary driving plates which are rotatable together, a pressure plate axially movable between the main and subsidiary driving plates through cooperation of spring and clutch release means, and a frictionengaging plate engageable on their opposite faces with the pressure plate and the subsidiary driving plate and secured to a clutch hub which is axially slidable on a transmission input shaft. The friction-engaging plate can be disengaged from the subsidiary driving plate completely and immediately when the clutch release means is so actuated.

United States Patent [1 1 Shono 1 Nov. 6, 1973 FRICTION-ENGAGING DEVICEPrimary ExaminerAllan D. Herrmann 75] Inventor: Kinji Sh0no,Wakoh,JapanAmmekmbe Bums [73] Assignee: Nissan Motor Co., Ltd., Kanagawaku,Yokohama, Japan [57] ABSTRACT Herein disclosed is a friction-engagingdevice such as a friction clutch for motor vehicle power transmissionsystems, having a flywheel which is made up of main and subsidiarydriving plates which are rotatable together, a pressure plate axiallymovable between the main and subsidiary driving plates throughcooperation of spring and clutch release means, and a frictionengagingplate engageable on their opposite faces with the pressure plate and thesubsidiary driving plate and secured to a clutch hub which is axiallyslidable on a transmission input shaft. The friction-engaging plate canbe disengaged from the subsidiary driving plate completely andimmediately when the clutch release means is so actuated.

4 Claims, 1 Drawing Figure 1 FRICTION-ENGAGING DEVICE This inventionrelates to friction-engaging devices and has particular reference tofriction clutches of the dry-disc type having a friction-engaging platewhich can be clamped between a driving member and a pressure plate whichis axially movable relative to the driving member. The friction-engagingdevice or'the friction clutch herein disclosed is specifically adaptedfor use in a motor vehicle power transmission system of thecounter-shaft type in which power delivered from an engine crankshaft isselectively transmitted to main and counterdrive shafts throughengagement of the frictionengaging device or clutch.

The friction clutches as usually employed in the motor vehicle powertransmission systems generally use a flywheel rotatable with the enginecrankshaft and a pressure plate drivingly connected to the flywheel soas to frictionally engage a driven element with the flywheel fortransmitting drive torque from the engine crankshaft to a transmissioninput shaft of the transmission system. The driven element is usually africtionengaging plate secured to a clutch hub which is splined to thetransmission input shaft and is frictionengageable with a back face ofthe flywheel and a front face of the pressure plate. The pressure plateis biased to a position in which the friction-engaging plate is held infriction engagement with the flywheel. When a clutch pedal for thetransmission system is depressed, the pressure plate is retracted fromthe frictionengaging plate by means of a suitable clutch releasemechanism so that the friction-engaging plate is disengaged from theflywheel, thereby interrupting the delivery of the power through theclutch. It is, in this instance, important that, when the pressure plateis released from the friction-engaging plate, the frictionengaging platebe completely free from contact with the flywheel so that no drivetorque is transmitted to the input shaft of the transmission system.

Where the friction clutches of the construction above outlined areincorporated in the power transmission systems of the counter-shafttype, a difficulty sometimes arises in that streamlined slindingengagement between the transmission input shaft and the clutch hubsupporting the friction-engaging plate is impaired especially after theclutches have been used for an extended period of time. This causes thefrictionengaging plate to fail to immediately and completely withdrawfrom the flywheel so that the transmission of the power through theclutch is continued even when the clutch pedal is in .a depressedcondition. Various attempts have thus far been made'to eliminate thedifficulty of this nature, none of such attempts having provedcompletely successful, however.

The power transmission system of the counter-shaft type has a main drivegear formed at an end of the input shaft and a counter gear formed onthe counter shaft and in constant mesh with the main drive gear. Themain drive gear is usually a left-hand helical gear while the countergear is a right-hand helical gear. When, therefore, the transmissionsystem is shifted from idling to forward drive condition, an axialthrust is imparted to the input shaft by reason of a tendency forcontinuous action along the helices of mating teeth of the two helicalgears. This thrust acts on the input shaft, which consequently is movedtoward the engine crankshaft. If, in this condition, the input shaftfails to freely slide on the clutch hub to which it is splined, then thefriction-engaging plate supported by the hub tends to move toward theflywheel. Rotation of the flywheel is thus objectionably transmitted tothe friction-engaging plate and accordingly to the input shaft eventhough the pressure plate is held in its retracted position.

When, thus, the clutch is dis-engaged and the transmission system isshifted to the forward drive condition from idling so that the motorvehicle is ready to start, a synchronizer of the transmission system isinoperable to have the main drive shaft properly synchronized with theinput shaft and, as a result, the shifting operation in the transmissionsystem can not be accomplished in a streamlined and reliable fashion.Granting, in this instance, that the synchronizer is capable ofoperating in a satisfactory condition, it will still happen that themotor vehicle is driven forward in an unforeseen unusual condition orthat the engine stops accidentally.

These problems will be solved if the helical main drive and countergears of the transmission system are substituted for usual spur gears sothat no axial thrust is imparted to the transmission input shaft. Theuse of the spur gears, however, creates other important problems such asthe degraded durability and generation of noises and, as such, are notpractically acceptable.

The problem of the improper or retarded disengagement of the clutch canalso be solved if the directions of the helix angles of the helicalgears are inversed, viz., if the main drive gear is a right-hand helicalgear and the counter gear is a left-hand helical gear. In this instance,the axial thrust resulting from the rotation of the helical gears isimparted to the input shaft in a reversed direction, viz., toward themain drive shaft so that difficulities are now encountered in how tobear such axial thrust within the power transmission system structure.In order that this axialthrust be borne within the transmission systemin a satisfactory condition, the power transmission system of thecounter-shaft type presently in common use will require extensive andsomewhat drastic changes and modification.

It is, therefore, an important object of this invention to provide animproved friction-engaging device, such as a friction clutch for motorvehicle power transmission systems, which can be completely and reliablydisengaged when it is desired to have the transmission of the drivetorque interrupted therethrough.

It is another important object of the invention to provide an improveddry-disc friction clutch which is specifically adapted for use in motorvehicle power transmission systems of the counter-shaft type.

It is a further object of the invention to provide an improved dry-discfriction clutch for the counter-shaft power transmission system usingusual helical gears for transmitting the drive torque from the inputshaft to the counter shaft, which clutch is capable of being disengagedimmediately and completely when the clutch pedal for the transmissionsystem is depressed during idling so as to establish forward drivecondition.

It is a still further object of the invention to provide an improveddry-disc clutch for the described motor vehicle power transmissionsystems, wherein the driven member or friction-engaging plate can bedisengaged from the engine flywheel completely and immediately when thepressure plate is retracted therefrom even though the friction-engagingplate is moved toward the flywheel due to the deteriorated slidingengagement between the transmission input shaft and the clutch hubspl-ined thereto.

It is a still further object of the invention to provide an improveddry-disc friction clutch for the described motor vehicle powertransmission systems in which the synchronizer forming an important partof the power transmission system is operable in a proper condition whenthe transmission system is shifted from the idling to the forward drivecondition.

According to this invention and to accomplish these and other objects,there is provided a friction-engaging device which comprisessubstantially concentrically aligned, rotatable members including a maindriving plate having at least one extension formed at its edge generallyin parallel to an axis of rotation of the driving plate, a subsidiarydriving plate 'which is secured at its edge to the above-mentionedextension of the main driving plate, the main and subsidiary drivingplates thus having their radial walls spaced apart from each other adistance approximately corresponding to the length of the aforesaidextension, a pressure plate positioned between and spaced apart from themain and subsidiary driving plates, an axially movable cover which issecured at its .edge to the pressure plate and which is positioned tocontain therein the subsidiary driving plate, and at least onefriction-engaging plate which is positioned between and engageable ontheir opposed sides with the subsidiary driving plate and the pressureplate. The pressure cover and the axially movable plate are movabletoward and away from the main driving plate so that the pressure plateis retracted from and pressed against the friction-engaging plate,respectively. Spring means is provided which, when maintained in aneutral condition, biases the axially movable cover away from thesubsidiary driving plate for causing the pressure plate to press thefriction-engaging plate against the subsidiary driving plate so that thefriction-engaging device in its entirety is held in a coupled condition.This condition is interrupted by actuation of clutch release means whichis provided in association with the aforesaid spring means. When thisclutch release means is actuated to an operative condition, then thespring means is forced to move the axially movable cover toward thesubsidiarydriving plate and accordingly move the pressure plate awayfrom the friction-engaging plate. The friction-engaging plate isconsequently disengaged from the subsidiary driving plate so that thepower train through the frictionengaging plate is cut off.

The spring means forming part of the device thus constructed may be aconed disc spring which is attached halfway to the axially movablecover. The coned disc spring is seated at one end on a back face of thesubsidiary driving plate and has its opposite end positioned to beengageable with the clutch release means which is above mentioned. Whenthe clutch release means is actuated and brought into engagement withthe coned disc spring, then the disc spring is forced toward thefriction-engaging plate so that the axially movable cover to which thespring is connected is moved together with the pressure plate toward themain driving plate.

The clutch release means, on the other hand, may comprise a clutchrelease bearing which is engageable with the aforesaid spring means suchas the coned disc spring and which is axially movable toward and awayfrom the friction-engaging plate. When the clutch release bearing isheld in a position remote from frictionengaging plate, the same isreleased from the spring means. The spring means thus assumes a neutralcondition. When the clutch release bearing is moved toward thefriction-engaging plate and engages with the spring means, then thespring means is forced toward the friction-engaging plate so as toestablish the uncoupled condition of the friction-engaging device.

Where the friction-engaging device which is constructed basically inthis manner is used as a friction clutch of a motor vehicle powertransmission system such as of the counter-shaft type, the main andsubsidiary driving plates constitutes, in combination, an engineflywheel and, as such, is rotatable with an engine crankshaft. In thisinstance, the friction-engaging plate is secured to a clutch hub whichis splined or keyed or otherwise axially movably connected to an inputshaft of the power transmission system. The clutch release means or,more specifically, the clutch release bearing is axially slidable overthe power tranmission input shaft and is operatively connected to aclutch pedal through a suitable mechanical linkage which may include aclutch release fork or withdrawal lever, as customary.

Other features and advantages of the frictionengaging device or, in amost practical form, the drydisc friction clutch in accordance with thisinvention will become more apparent from the following detaileddescription given by way of example with reference to the accompanyingdrawing which illustrates, in a longitudinal axial section, a motorvehicle power transmission system of the counter-shaft type includingthe friction clutch according to this invention in a preferred form.Before entering into detailed discussion of the device according to theinvention, itis to be noted that the device may be either of thesingle-disc or multipledisc type although the same will be hereindescribed and shown as being of the former type.

Referring to the drawing, the friction clutch according to the inventionas shown forms part of a motor vehicle power transmission system of thecounter-shaft type which includes a crankshaft l driven from a motorvehicle engine, not shown, and an input shaft 2 having a pilot endportion 2a extending into an axial bore la in the crankshaft 1. Theinput shaft 2 is rotatable relative to the crankshaft 1 through a pilotbearing 3, as usual. A flywheel 4 as a main driving plate is connectedto the crankshaft 1 through a bolt 5 or any other fastening means so asto be rotatable therewith. The flywheel 4 has at its peripheral edge atleast one extension 40 which is generally in parallel to the input shaft2. It is preferable that the extension 4a is provided as three in numberthough not so shown. A generally annular driving member 6 as asubsidiary driving plate is secured at its edge to the flywheel 4 bymeans of a bolt or bolts 7. The flywheel 4 and annular driving member 6are thus rotatable together with the crankshaft l.

A clutch hub 8 having a radial extension or flange portion, notnumbered, is splined as at 9 to the trans mission input shaft 2 so as tobe axially movable thereon. This clutch hub 8 supports afriction-engaging plate which is generally denoted by reference numeral10. The friction-engaging plate 10 is usually made up of clutch discmounts 11 and 11' secured to both faces of the flange portion of theclutch hub 8 by bolts or rivets 12, a clutch disc or cushioning plate 13radially extending from the clutch disc mount 11, and a pair of clutchfriction facings 14 and 14' which are rivetted or bonded to both sidesof the cushioning plate 13. The facings 14 and 14" are usually in anannular form and one of them, which may be the facing 14', is sopositioned as to be friction-engageable with the annular driving member6 when the friction-engaging plate 10 is in an operative position whichis illustrated.

A pressure plate is located between the flywheel 4 and thefriction-engaging plate 10 so as to be frictionengageable with thefacing 14 of the friction-engaging plate. The pressure plate 15 ismounted on an axially movable clutch cover 16 through bolts 17, theclutch cover thus containing therein the annular member 6 and thefriction-engaging plate 10, as shown. When, thus, the axially movableclutch cover 16 is moved away from the flywheel 4, the pressure plate 15is forced against the friction facing 14 and accordingly the otherfacing 14' is pressed upon the annular driving member 6 so that therotation of the annular driving member 6 is followed by thefriction-engaging plate 10 and consequently by the clutch hub 8.

Such axial movement of the clutch cover 16 is effected throughcooperation of a coned disc spring 18 and a clutch release bearing 19.The coned disc spring 18 is located to be intermediate between theannular member 6 and a radial wall portion of the clutch cover 16 andsecured halfway to the clutch cover through a thrust rivet 20 which isloaded by thrust rings 21 and 21. This coned disc spring 18 has itsouter peripheral edge seated on the back face, shown as backwardlyprotruded at 60, of the annular driving member 6 and its innerperipheral edge surrounding the transmission input shaft 2 behind theclutch hub 8, whereby the axially movable clutch cover 16 is biased awayfrom the annular member 6 so that the frictionengaging plate 10 ismaintained in friction-engagement with the annular member. The clutchrelease bearing 19, on the other hand, is located to be engageable withthe inner peripheral edge portion of the coned disc spring 18 and issupported on a sleeve 22 which is positioned over the transmission inputshaft 2, as shown. This sleeve 22 is axially movable toward and awayfrom the coned disc spring 18 by means of a clutch release fork 23 whichis operatively connected to a clutch pedal, not shown. When, thus, thesleeve 22 is held in a position remote from the coned disc spring 18,the clutch release bearing 19 is disengaged from the disc spring, whichconsequently is maintained in its neutral condition. When, on thecontrary, the sleeve 22 is moved by the clutch release fork 23 towardthe coned disc spring 19 and the clutch release bearing 18 is broughtinto abutting engagement with the disc spring, the disc spring is forcedtoward the flange portion of the clutch hub 8 as indicated by brokenlines 80 that the clutch cover 16 and accordingly the pressure plate 15are moved toward the flywheel 4, thereby causing the friction-engagingplate 10 to be uncoupled from the annular driving member or subsidiarydriving plate 6 so as to interrupt the delivery of the power from theflywheel 4 to the transmission input shaft 2.

The transmission input shaft 2 is associated with a main drive shaft 24which is in line with the input shaft 2 and a counter shaft 25 extendingin parallel to the main drive shaft 24. The main drive shaft 24 andcounter shaft 25 are accommodated within a transmission housing 26 whichrotatably supports the transmission input shaft 2 through a bearing 27.The transmission input shaft 2 has formed at its rear end a main drivegear 28 which is in constant mesh with a counter gear 29 which is formedon the counter shaft 25 as shown. The main drive gear 28, as previouslynoted, a usual left-hand helical gear while the counter gear 29 is aright-hand helical gear. Designated generally by reference numeral 30 isa synchronizer unit whereby the rotation of the transmission input shaft2 is transmitted to the main drive shaft 24 in synchronism.

When, thus, the clutch pedal is depressed'and consequently the clutchrelease bearing 19 is caused to press upon the coned disc spring 18 soas to establish the forward drive condition from idling, thefriction-engaging plate 10 is permitted to completely and immediatelywithdraw from the annular driving member 6 as the susidiary drivingplate even though the clutch hub 8 fails to freely slide on thetransmission input shaft 2 which is urged toward the engine crankshaft lby reason of the helix angles of the gears 28 and 29. Improper orretarded disengagement of the clutch as conventionally encountered canbe avoided in this manner while, at the same time, the transmissionsynchronizer does operate in a proper condition.

What is claimed is:

1. A friction-engaging device comprising, substantially concentricallyaligned rotatable members including a main driving plate having at leastone extension formed at its edge substantially in parallel to an axis ofrotation of said main driving plate and a subsidiary driving platesecured at its edge to said extension of the main driving plate, themain and subsidiary driving plates thus having their radial walls spacedapart from each other, a pressure plate positioned between and spacedapart from said main and subsidiary driving plates, an axially movablecover secured at its edge to said pressure plate and positioned tocontain therein said subsidiary driving plate, and at least onefrictionengagirig plate positioned between and engageable on theiropposite sides with said subsidiary driving plate and said pressureplate, said pressure plate and said axially movable cover being movabletogether toward and away from said main driving plate for causing thepressure plate to be retracted from and pressed against saidfriction-engaging plate respectively; spring means having a neutralposition to bias said axially movable cover away from said subsidiarydriving plate and release means engageable with said spring means forcausing the spring means to be retracted from said neutral position.

2. A friction-engaging device according to claim 1, in which said springmeans comprises a coned disc spring located intermediate said subsidiarydriving plate and said axially movable plate and secured halfway to saidaxially movable cover, said coned disc spring having an outer peripheraledge seated on said subsidiary driving plate and an inner peripheraledge positioned to be engageable with said release means.

3. In a power transmission system of the described counter-shaft type, afriction clutch which comprises a fly-wheel rotatable with an enginecrankshaft and having at least one extension formed at its edgesubstantially in parallel to an axis of rotation of said flywheel, anannular driving member secured at its outer edge to said extension ofsaid flywheel, said flywheel and said annular driving member thus havingtheir radial walls spaced apart from each other a distance substantiallycorresponding to the length of said extension, a clutch hub 'axiallymovable on and rotatable with a transmission input shaft extending inline with said crankshaft, a friction-engaging plate secured to andradially extending from said clutch hub, a pressure plate positionedbetween said flywheel and said friction-engaging plate, an axiallymovable clutch cover secured at its edge to said pressure plate andcontaining therein said annular driving member and saidfriction-engaging plate, said pressure plate and said clutch cover beingaxially movable together toward and away from said flywheel forrespectively causing said pressure plate to be retracted from andpressed upon said frictionengaging plate, said friction-engaging platehaving friction facings which are respectively brought into frictionengagement with said pressure plate and said annular driving member whensaid pressure plate is pressed upon said friction-engaging plate, springmeans having a neutral position in which said axially movable clutchcover is biased away from said annular driving member, and clutchrelease means which is engageable with said spring means for causing thespring means to be retracted from said neutral position.

4. A friction clutch according to claim 3, which said spring meanscomprises a coned disc spring located intermediate between said annulardriving member and said clutch cover and secured halfway to a radialwall portion of said clutch cover, said disc spring having an outerperipheral edge seated on said annular driving member and an innerperipheral edge surrounding said transmission input shaft so as to beengaged by said clutch release means when the clutch release means isactuated.

1. A friction-engaging device comprising, substantially concentricallyaligned rotatable members including a main driving plate having at leastone extension formed at its edge substantially in parallel to an axis ofrotation of said main driving plate and a subsidiary driving platesecured at its edge to said extension of the main driving plate, themain and subsidiary driving plates thus having their radial walls spacedapart from each other, a pressure plate positioned between and spacedapart from said main and subsidiary driving plates, an axially movablecover secured at its edge to said pressure plate and positioned tocontain therein said subsidiary driving plate, and at least onefriction-engaging plate positioned between and engageable on theiropposite sides with said subsidiary driving plate and said pressureplate, said pressure plate and said axially movable cover being movabletogether toward and away from said main driving plate for causing thepressure plate to be retracted from and pressed against saidfriction-engaging plate respectively; spring means having a neutralposition to bias said axially movable cover away from said subsidiarydriving plate and release means engageable with said spring means forcausing the spring means to be retracted from said neutral position. 2.A friction-engaging device according to claim 1, in which said springmeans comprises a coned disc spring located intermediate said subsidiarydriving plate and said axially movable plate and secured halfway to saidaxially movable cover, said coned disc spring having an outer peripheraledge seated on said subsidiary driving plate and an inner peripheraledge positioned to be engageable with said release means.
 3. In a powertransmission system of the described counter-shaft type, a frictionclutch which comprises a fly-wheel rotatable with an engine crankshaftand having at least one extension formed at its edge substantially inparallel to an axis of rotation of said flywheel, an annular drivingmember secured at its outer edge to said extension of said flywheel,said flywheel and said annular driving member thus having their radialwalls spaced apart from each other a distance substantiallycorresponding to the length of said extension, a clutch hub axiallymovable on and rotatable with a transmission input shaft extending inline with said crankshaft, a friction-engaging plate secured to andradially extending from said clutch hub, a pressure plate positionedbetween said flywheel and said friction-engaging plate, an axiallymovable clutch cover secured at its edge to said pressure plate andcontaining therein said annular driving member and saidfriction-engaging plate, said pressure plate and said clutch cover beingaxially movable together toward and away from said flywheel forrespectively causing said pressure plate to be retracted from andpressed upon said friction-engaging plate, said friction-engaging platehaving friction facings which are respectively brought into frictionengagement with said pressure plate and said annular driving member whensaid pressure plate is pressed upon said friction-engaging plate, springmeans having a neutral position in which said axially movable clutchcover is biased away from said annular driving member, and clutchrelease means which is engageable with said spring means for causing thespring means to be retracted from said neutral position.
 4. A frictionclutch according to claim 3, which said spring means comprises a coneddisc spring located intermediate between said annular driving member andsaid clutch cover and secured halfway to a radial wall portion of saidclutch cover, said disc spring having an outer peripheral edge seated onsaid annular driving member and an inner peripheral edge surroundingsaid transmission input shaft so as to be engaged by said clutch releasemeans when the clutch release means is actuated.